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Honeybee problems explained

A parasitic mite has helped a virus wipe out billions of honeybees throughout the globe, say scientists.
A team studying honeybees in Hawaii found that the Varroa mite helped spread a particularly nasty strain of a disease called deformed wing virus.
The mites act as tiny incubators of one deadly form of the disease, and inject it directly into the bees' blood.
This has led to "one of the most widely-distributed and contagious insect viruses on the planet".
The findings are reported in the journal Science.
The team, led by Dr Stephen Martin from the University of Sheffield, studied the honeybees in Hawaii, where Varroa was accidentally brought from California just five years ago.
Crucially some Hawaiian islands have honeybee colonies that are still Varroa-free.

This provided the team with a unique natural laboratory; they could compare recently-infected colonies with those free from the parasite, and paint a biological picture of exactly how Varroa affected the bees.
The team spent two years monitoring colonies - screening Varroa-infected and uninfected bees to see what viruses lived in their bodies.
Dr Martin explained to BBC Nature that most viruses were not normally harmful to the bees, but the mite "selected" one lethal strain of one specific virus.
"In an infected bee there can be more viral particles than there are people on the planet," Dr Martin explained.
"There's a vast diversity of viral strains within a bee, and most of them are adapted to exist in their own little bit of the insect; they get on quite happily."
But the mite, he explained, "shifts something".
In Varroa-infected bees, over time, the vast majority of these innocuous virus strains disappear and the bees' bodies are filled with one lethal strain of deformed wing virus.
And when it comes to viral infection, it's the sheer quantity that kills; each viral particle invades a cell and takes over its internal machinery, turning the bee's own body against itself.
Although it is not clear exactly why this strain thrives in mite-infected bees, Dr Martin explained that it could be the one virus best able to survive being repeatedly transmitted from the mites to the bees and back, as the mites feed on the bees' blood.
The effect appears to take once the mites have changed this "viral landscape" in the bees' bodies, the change is permanent.
"So the only way to control the virus is to control the levels of the mite," said Dr Martin.

The current Varroa-adapted DWV variants will continue
to evolve, and investigations of virus strain
differences may explain the different pathologies
currently seen globally in honey bee colonies
(7). Such variants may interact with other pests,
pathogens, environmental factors, and regional
beekeeping practices, resulting in recent largescale
losses of honey bee colonies (6). This study
shows that the spread of Varroa in Hawaii has
caused DWV, originally an insect virus of low
prevalence, to emerge. This association may be
responsible for the death of millions of colonies
worldwide wherever Varroa and DWV co-occur.

Doris, please confine your anti-neonicotinoid campaigning to the 'Beekeeping and the Environment' area.

I reckon that the DWV as carried by the varroa mite can survive in bees even after the varroa in that hive have been eliminated. If the level of varroa infestation was high then the level of virus will be high too and in a colony treated for varroa which has a high level of DWV going into the winter the chances of survival will be much lower. It is important then to keep the varroa level in the pre-autumn period low and to get to this state as soon as possible after the honey flow to allow a population of DMV free bees to emerge and bring the colony through the winter. The kentics of DMV i'm sure is a balancing act between bees being born and bees being infected, the more bees being born in the absense of varroa reducing virus levels to a safer winter level ? Thymol based products do work but must be applied sooner than later (Sept might be too late) esp if you are in northern Ireland or Scotland